XMLHttpRequest.send()

The XMLHttpRequest method send() sends the request to the server. If the request is asynchronous (which is the default), this method returns as soon as the request is sent and the result is delivered using events. If the request is synchronous, this method doesn't return until the response has arrived.

send() accepts an optional parameter which lets you specify the request's body; this is primarily used for request such as PUT. If the request method is GET or HEAD, the body parameter is ignored and request body is set to null.